We intend to study the induction of specific immunological tolerance and the generation as well as the transfer of suppressor cell activity in cultures of lymphoid cells from rabbits and rats. We shall seek to solidify our understanding of a system in which antibody formation against solubilized bacteriophage antigens provides a model for a response in which antibody formation is independent of help by macrophages or T cells but is susceptible to inhibition by either receptor blockade or suppressor cells. The nature and mode of action of suppressor cells will be studied to gain information on how they can be controlled. We also intend to test the hypothesis that immunogenic doses of antigen may induce suppressor cell activity concurrently with inciting formation of antibody. A possible helper role of tolerized B cells in the generation of T suppressor cells will be examined. Further experience gained in this model will be applied to in vitro and in vivo studies in inbred rats and extended to studies on in vitro responses of rats to tumor associated antigens in syngeneic systems. We believe that insights gained through the proposed work may provide an improved approach to the management of allergic or autoimmune diseases and attempts at immunotherapy of cancer in man.